The present invention relates to a linkage device of an internal combustion engine, and more particularly to a linkage device through which a pair of drive shafts for operating swirl control valves in a V-type engine are rotated by reciprocating-motion generated by an actuator.
Japanese Patent Provisional Publication No. 6-173695 discloses an intake system for an in-line four-cylinder internal combustion engine which device is provided with swirl control valves for controlling in-cylinder air flow such as swirl and tumble of air. These swirl control valves are connected to a common drive shaft which is directly rotated by an actuator. An engine control unit outputs a drive signal determined by an engine operating condition such as load, engine rotation speed and engine temperature to the actuator in order to control the opening of the swirl control valves. If such an intake system is employed in a V-type engine, it is necessary to prepare two drive shafts for respectively operating swirl control valves of two banks of the V-type engine. In order to operate the two drive shafts, it is necessary to provide two actuator or to provide one actuator for directly operating one drive shaft and a linkage device for operating the other drive shaft utilizing the drive power of the actuator.
However, in such arrangements, the actuator is protrudedly installed at end portions of the drive shafts. Such an engine system with this conventional device requires large space, and therefore the total length or height of the engine system may become large. Further, in case that the drive shafts are directly driven by the respective actuators, each of the drive shafts is fixedly connected to each actuator so as not to generate play therebetween. Therefore, if a temperature difference occurs in the engine in the longitudinal direction, the drive shaft may be twisted and therefore the openings of the swirl control valves become different. This opening difference causes the dispersion of the swirls among the combustion chambers of the engine and the degradation of the combustion. Consequently, the performance of the engine may be degraded. Further, in case that one of the two drive shafts is directly driven by the actuator and the other drive shaft is driven by the actuator through a linkage device, it is difficult to synchronize the rotations of the two drive shafts. That is, the operation of the other drive shaft driven through the linkage device is delayed by play caused by the linkage device as compared with the drive shaft directly driven by the actuator. Therefore, the opening of the swirl control valves for one bank becomes different from that of the swirl control valves for the other bank. This dispersion among the openings of the valves causes the dispersion among the swirls in the combustion chambers of the engine and the degradation of the combustion.